This invention relates generally to the preparation of structures for use in semiconductor applications and relates, more particularly, to the formation of thin films upon a substrate.
The film-growth materials with which this invention is concerned includes alkaline earth oxides, such as BaO, SrO, CaO and MgO, which each have a sodium chloride-type lattice structure. Silicon similarly has a face-centered-cubic lattice structure, and the match between lattice parameters of silicon and the aforelisted oxides promote the epitaxial growth of film layers of the oxides upon the surface of silicon.
While the match between lattice parameters of silicon and any of the aforementioned alkaline earth oxides is relatively close, any mismatch between lattice parameters of adjacent layers can spawn lattice strain at the interface of the adjacent layers, and such strain may lead to the development of dislocations or other undesirable defects at the interface. It would therefore be desirable to provide a process for growing epitaxial layers with materials having sodium chloride-type lattice structures and wherein lattice strain at the interface of adjacent layers is appreciably reduced or, in the alternative, virtually eliminated.
Accordingly, it is an object of the present invention to provide a new and improved process of depositing an epitaxial layer of alkaline earth oxide upon another layer having an ordered face-centered-cubic lattice structure like that of silicon or an alkaline earth oxide having a sodium chloride-type lattice structure wherein lattice strain between adjacent layers is reduced or eliminated and a structure formed with the process.
Another object of the present invention is to provide such a process wherein the interfacial coherence and crystalline quality at the interface between adjacent layers of the resulting structure is improved.
Yet another object of the present invention is to provide such a process which can be used for epitaxially growing an alkaline earth oxide upon a base layer of silicon or upon a base layer of another alkaline earth oxide.
Still another object of the present invention is to provide such a process which is well-suited for growing an epitaxial film of MgO upon a silicon substrate.